Re: [RFC][PATCH v2 02/12] diglim: Basic definitions

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Jul 26, 2021 at 06:36:50PM +0200, Roberto Sassu wrote:
> --- /dev/null
> +++ b/include/uapi/linux/diglim.h
> @@ -0,0 +1,51 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
> + *
> + * Author: Roberto Sassu <roberto.sassu@huawei.com>
> + *
> + * DIGLIM definitions exported to user space, useful for generating digest
> + * lists.
> + */
> +
> +#ifndef _UAPI__LINUX_DIGLIM_H
> +#define _UAPI__LINUX_DIGLIM_H
> +
> +#include <linux/types.h>
> +#include <linux/hash_info.h>
> +
> +enum compact_types { COMPACT_KEY, COMPACT_PARSER, COMPACT_FILE,
> +		     COMPACT_METADATA, COMPACT_DIGEST_LIST, COMPACT__LAST };
> +
> +enum compact_modifiers { COMPACT_MOD_IMMUTABLE, COMPACT_MOD__LAST };
> +
> +enum compact_actions { COMPACT_ACTION_IMA_MEASURED,
> +		       COMPACT_ACTION_IMA_APPRAISED,
> +		       COMPACT_ACTION_IMA_APPRAISED_DIGSIG,
> +		       COMPACT_ACTION__LAST };
> +
> +enum ops { DIGEST_LIST_ADD, DIGEST_LIST_DEL, DIGEST_LIST_OP__LAST };
> +
> +/**
> + * struct compact_list_hdr - header of the following concatenated digests
> + * @version: version of the digest list
> + * @_reserved: field reserved for future use
> + * @type: type of digest list among enum compact_types
> + * @modifiers: additional attributes among (1 << enum compact_modifiers)

I do not understand this description, what does it mean?

> + * @algo: digest algorithm

Is this also a #define or an enum?  Where is the list of them?

> + * @count: number of digests
> + * @datalen: length of concatenated digests

Where does this count and length come into play as nothing else is in
this structure?

> + *
> + * A digest list is a set of blocks composed by struct compact_list_hdr and
> + * the following concatenated digests.
> + */
> +struct compact_list_hdr {
> +	__u8 version;
> +	__u8 _reserved;

You MUST check this for 0 today, and document it above.  If not, you can
never use it in the future.

> +	__le16 type;
> +	__le16 modifiers;
> +	__le16 algo;
> +	__le32 count;
> +	__le32 datalen;
> +} __packed;
> +#endif /*_UAPI__LINUX_DIGLIM_H*/
> -- 
> 2.25.1
>